This assay is performed using the Diagnostica Stago LIATEST Protein S Kit on the Beckman Coulter ACL TOP. Protein S total antigen is determined using automated latex immunoassay methodology. This methodology is comprised of a reagent with microlatex particles coated with specific antihuman total protein S antibodies. Patient plasma containing total protein S antigen is combined with the latex reagent causing the antibody-coated latex particles to agglutinate and form aggregates. The aggregates form diameters greater than the wavelength of the light (405 nm) passing through causing absorption of the light. This change in absorption is measured over time and reported as delta optical density (OD). The increase in absorption is proportional to the concentration of protein S total antigen present in the patient plasma.

Free:

This assay is performed using the HemosIL Free Protein S kit on the Beckman Coulter ACL TOP. The assay uses latex immunoassay methodology to determine the presence of free protein S. It consists of 2 latex reagents, one being latex particles coated with purified human C4BP and the other is latex particles coated with a monoclonal antibody directed against human protein S. Patient plasma is combined with the purified C4BP which reacts with a high affinity for free protein S in the patient plasma. The free protein S adsorbed on the C4BP latex triggers the agglutination reaction with the second latex reagent. The aggregates form diameters greater than the wavelength of the light (405 nm) passing through causing absorption of the light. This change in absorption is measured over time and reported as delta OD. The increase in absorption is proportional to the concentration of free protein S antigen present in the patient plasma.